In recent years, health preference is being enhanced, and it is required that foods and drinks are taken and, at the same time, an active ingredient which enhances health can be ingested. For this reason, an attempt to add various active ingredients to foods or drinks has been tried. However, among these active ingredients, there are some having a peculiar smell, such as yeast. In addition, there are an active ingredient which deteriorates a taste of foods or the like when directly added to foods or drinks, and an active ingredient which is degraded or denatured by an ingredient contained in foods or the like, such as DHA (docosahexaenoic acid). In such the case, a method of encapsulating an active ingredient with being contained in a capsule filler solution, and adding this to foods or drinks is useful. As a covering film matrix for a capsule, gelatin is generally used frequently. Gelatin is prepared mainly from a bone, a cartilage, a skin and a tendon of an animal.
However, since gelatin is inferior in heat resistance, there is a disadvantage that when foods or drinks with a capsule added thereto are sterilized at an elevated temperature, a capsule covering film is dissolved, and a capsule filler solution is dissolved out into foods or drinks. Further, in recent years, since there is a tendency that a raw material derived from an animal is not preferred, use of a non-protein-based capsule covering film matrix which does not contain gelatin derived from an animal has been initiated to be desired. As the non-protein-based capsule covering film matrix, for example, agar and sodium alginate are known.
Although agar is an alga-processed product, and is not a raw material derived from an animal, it has not such the sufficient heat resistance that can endure the sterilizing condition at an elevated temperature of 80° C. or higher, and has a defect that it is inferior in processibility into foods or the like. In addition, since an agar gel is fragile, and is inferior in elasticity, a physical strength as a capsule covering film matrix is not sufficient.
A method of adding a divalent ion such as a calcium ion to enhance heat resistance of a capsule covering film in the case of using sodium alginate as a capsule covering film matrix is known. However, this method has a defect that heat resistance is not enhanced due to ion dissociation in the presence of a chelating agent and, for this reason, a kind of a capsule filler solution which can be used may be limited.
Japanese Patent Application Laid-Open (JP-A) No. 2003-79351 proposes a capsule for a drink excellent in heat resistance, containing gellan gum which is a polysaccharide, as a covering film component of a microcapsule. However, when a covering film is formed using gellan gum as a covering film component, an ion bond such as a calcium ion is accompanied as in formation of a covering film of the aforementioned sodium alginate. Therefore, there is a defect that, when a chelating agent having the ion dissociating activity is present, a heat resistant covering film cannot be formed. In addition, since gellan gum exhibits such the gel property that it has no elastic force and is fragile and easily ground like agar, gellan gum is suitable in block massy products such as jelly, but has a defect that a physical strength in the thin film state such as a capsule covering film is low, and gellan gum is easily disintegrated at preparation of a capsule, and a yield is deteriorated.